Today, a wide variety of applications demand that a workstation display a moving image with accompanying sound. Often these workstations must access the audio and video data from multiple sources, some local and some accessed via a network connection. This data must be supplied to the display unit at a constant rate in order to achieve a steady picture. Problems arise when the data is not provided to the workstation at the required rate.
This problem is particularly acute when the data source must be accessed via a network. Delays in accessing data over standard networks tend to be longer and have a wider variance than accessing data from a local source (e.g., local RAM, local disk drive). Conventionally, one must insure that the network provides the data at a constant rate in order to achieve an acceptable output.
One way of achieving a constant data rate is known as the “server push” solution. In a system implemented with the “server push” model, the client sends a request specifying what to play, and how fast to play it. The server responds by sending the requested information at the requested rate. One advantage of the “server push” solution that the client hardware and software required is very simple.
That approach, however, has several drawbacks. First, in “server push” systems, the client sends requests to the server when the user issues a playback control signal, such as “play”, “stop,” or “fast forward.” The user, however, cannot specify a particular frame or frames to be played because the playback logic resides within the server. Applications that lack frame accurate playback capability may be sufficient for most users. However, those applications cannot meet the demand of developers and artists for creating animation and special effects. Therefore, there exists a need for an improved system and method of providing frame-accurate transport of media data across a data network.
Further, in “server push” systems, it is not possible to play multiple clips seamlessly across the network if the clips are stored in different locations. Usually, after each clip is played, the user has to manually select another clip to be played. In other cases where a playlist is specified, there is usually a short “break” between the ending of one clip and the beginning of another. This is caused by the fact that the client workstation has no control over when the movie data is sent. Thus, there exists a need for a system and method of providing seamless playback of multiple clips across a data network.